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Home/Anthropology/Mains PYQ/2016/Paper I/Human Genetics & Human Biology
UPSC MainsAnthropology Optional Paper I 2016 15 Marks Model Answer Available

Mendelian Principles and Their Application to Human Populations — 2016 Paper I

Question · 2016 · Paper I · 15 Marks

Critically discuss the Mendelian principles and their application to human populations.

Model Answer

VAID ICS

 Approach

  • Demand of Question: State Mendelian principles accurately, apply them to human pedigrees/populations, and critically show where simple Mendelian ratios fail.
  • Structuring the Response: Segregation/dominance/independent assortment -> human disorder examples -> pedigree/population applications -> Hardy-Weinberg link -> molecular applications -> non-Mendelian complexities.
  • Key Dimensions to Cover: Mendel (1866); autosomal dominant/recessive; X-linked; codominance ABO; linkage; pedigrees; carrier frequency; penetrance, expressivity, epistasis, imprinting, polygenic traits.

Model Answer

Introduction

Mendel’s experiments, published in 1866, established principles of particulate inheritance that remain foundational for analysing many human traits, although human inheritance often departs from simple Mendelian ratios.

Body

The law of segregation states that the two alleles at a locus separate during gamete formation, so an offspring receives one allele from each parent. This explains autosomal recessive disorders such as sickle-cell disease and phenylketonuria and autosomal dominant disorders such as Huntington disease. The principle of dominance describes phenotypic expression in heterozygotes but is not universal: codominance is seen in ABO alleles and incomplete dominance occurs in other systems. Independent assortment applies to genes on different chromosomes, or sufficiently far apart on the same chromosome; linkage limits its universality.

Because controlled crosses are impossible in humans, Mendelian analysis is applied through pedigrees, twin/family studies and molecular testing. Pedigrees permit inference of dominant, recessive, X-linked and mitochondrial inheritance and estimation of recurrence risk. Population genetics extends Mendelian principles through Hardy-Weinberg expectations, allowing estimation of carrier frequencies and testing whether forces such as selection, migration, drift or assortative mating are operating.

Applications include carrier detection for thalassaemia and sickle-cell disorders, paternity exclusion, genetic counselling and interpretation of blood-group polymorphisms. Mendelian logic also underlies linkage mapping and gene identification.

However, most human phenotypes—stature, skin pigmentation, blood pressure or diabetes risk—are polygenic and environmentally modified. Penetrance, variable expressivity, epistasis, genomic imprinting and epigenetic effects further complicate prediction.

Conclusion

Thus, Mendelian principles provide the baseline grammar of human inheritance; their strongest application lies in analysing identifiable loci and pedigrees, while population and molecular genetics explain the more complex architecture of human variation.

2026 Genetic polymorphism and natural selection. 2026 Numerical chromosomal aberrations can be due to abnormalities in autosomes as well as sex chromosomes. Elaborate in terms of the effects these have on human body, giving suitable examples. 2026 Distinguishing features of nuclear and mitochondrial DNA. 2026 How would you find out that a particular disease/disorder is inherited and, if so, in which manner? Elaborate with suitable examples.

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UPSC Anthropology Optional 2016 — Paper I

28 questions

1(b) Cultural Relativism

10 Marks150 words
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10 Marks150 words
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2016Paper IHuman Genetics & Human BiologyModel answer available

5(e) Forensic Anthropology

10 Marks150 words
Syllabus: Paper I > 12. Applications of Anthropology > Forensic Anthropology
2016Paper IApplied & Forensic AnthropologyModel answer available

1(e) Functionalism

10 Marks150 words
Syllabus: Paper I > 6. Anthropological Theories > Functionalism
2016Paper IAnthropological TheoriesModel answer available

1(c) Lineage and Clan

10 Marks150 words
Syllabus: Paper I > 2.5 Kinship > Descent groups > Lineage and clan
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5(c) Neolithic Cultures of India

10 Marks150 words
Syllabus: Paper I > 1.8(b) Cultural Evolution: broad outlines of prehistoric cultures > Neolithic
2016Paper IPrehistoric ArchaeologyModel answer available

5(a) Rh-Blood Group

10 Marks150 words
Syllabus: Paper I > 9.6 Population variation as genetic marker > ABO and Rh blood groups
2016Paper IHuman Genetics & Human BiologyModel answer available

5(b) Rhodesian Man

10 Marks150 words
Syllabus: Paper I > 1.6 Phylogenetic status, characteristics and distribution > Rhodesian Man
2016Paper IHuman Evolution & PrimatologyModel answer available

1(d) Totemism

10 Marks150 words
Syllabus: Paper I > 5. Religion > Forms of religion > Totemism
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